Ball screw



FIG. 1 is a front and right side perspective view of a ball screw;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a bottom view thereof;

FIG. 8 is an enlarged view taken along line 8-8 in FIG. 2; and,

FIG. 9 is an enlarged schematic cross-sectional view thereof taken along line 9-9 of FIG. 2.

The broken lines in the drawing represent the environment of the claimed design and form no part thereof. 

CLAIM The ornamental design for a ball screw, as shown and described. 